Choke control mechanism for carburetors



Jan. 17,1939. E. COFFEY 2,144,352

CHOKE CONTROL MECHANISM FOR CARBURETORS Filed May 18, 1957 a 1''" II "I 24 A IN VENT'OE HTTOBNEY Patented Jan. 17, 1939 CHOKE CONTROL MECHANISM FOR CARBURETORS Irven E. Coffey, St.'Louis, Mo., assignor to Carter Carburetor Corporation, St. Louis, Mo., a corporation of Delaware Application May 18, 1937, Serial No. 143,266 2 Claims. (Cl. 123-119) This invention relates particularly to automatic choke mechanisms for internal combustion engine carburetors.

V such mechanisms usually embody a ta -tam which, when cold, closes the choke and which is enclosed in a suitable housing. In some cases.

the thermostat housing is carried directlyby-the carburetor and is spacedsubstantially from the.

hotter portions of the engine. Heat is supplied to the housing from a suitable stove, mounted usually on the engine exhaust manifold and circulation of the heated gases past the thermostat is produced by a suction connection between the housing and the intake manifold or carburetor. With this arrangement the rate the heated gases are drawn through the housing and, consequently, the temperature of the thermostat, depends in part upon the suction in the intake manifold. When subnormal suctions prevail in the intake manifold for a substantial period as, for instance, when the engine is subjected to a heavy load with the throttle substantially opened, the temperature of the thermostat may drop sufliciently to partially close the choke valve, thus producing an undesirable restriction in the carburetor mixture conduit. This, in turn, would unduly enrich the mixture and reduce the power of the engine.

An object of the present invention is to provide means for preventing an excessive drop in the temperature of the choke controlling thermostat during operation of the engine. A more detailed object is to provide a suction booster device in combination with a thermostat housing of the above type for insuring an adequate flowof heated gases through the thermostat housing at all times. These objects and other more detailed objects hereafter appearing are attained. substantially by the structure illustrated in which The figure shows portions of an internal combustion engine including the carburetor, parts of the manifolds, and parts of a combination suction booster and fuel pump device. 7

The carburetor shown includes an air' horn I and barrel 2 forming a downdraft mixture passage and is flanged at 3 for attachment to the hot spot portion 4 of the manifold'construction by means of bolts 5. The hot spot construction, wherein a portion of the heat from the exhaust gases is transferred to the intake mix ture, is ofbox-shape and'connects at each end with horizontally aligned intake manifold 6 and exhaust manifold 1. Any suitable hot spot structure may be used or, if desired, such struci ture may be omitted.

A choke valve (not shown) is pivotally mounted in theupper portion of the mixture conduit on a suitable shaft which projects beyond the carburetor barrel and inside of an insulated housing 8 mountedon the air horn. An arm 9 is rigid 5 with the end of the choke shaft in housing 8 and has lateralfinger at its outer end engaged bya hook H at the outer end of coiled bi-metal thermostat |2. The inner end of the thermostat is secured toa pintle l3 projecting from the 10 outer wall or cover of the housing. Also rigidly connected with the choke shaft and arm-"9 is a curved crank I4 connected by a link IS with a piston" l6 slidably received in a small cylinder formed in the thermostat housing. A stove l8 16 mounted on exhaust manifold l is connected by means of a tube I9 to the interior of housing 8 for supplying heated gases thereto.

Also carried on a suitable portion of the engine is a suction booster device generally indicated at 20 20. This device includes a flexible diaphragm 2| constantly urged downwardly by coiled spring 22 and connected through a hanger link 23 and rock arm 24 with a cam 25 on the usual engine cam shaft 26. A second rock arm 21 is also actuated 26 from cam 25 and connected by means of a hanger link 28 with a fuel pump (not shown), which may be of any well known construction. The booster device has a central partition 29 forming chambers 30 and 3|, the latter enclosing diaphragm 30 2|. Chamber 30 has threaded inlet connections 32 and 33 and chamber 3| has a threaded outlet connection 34. A tube 35 connects inlet 33 with a windshield wiper 36 and a tube 31 connects inlet 32 with cylinder l1 in the thermostat hous- 35 ing'. Outlet connection 34 is connected to the intake manifold by means of a tube 38.

Chambers 30 and 3| and threaded outlet 34 are connected by passages 39 and 40 controlled, respectively, by spring pressed inlet and outlet 40 checks 4| and 42. The check valves and suction pump arrangement are so constructed that when the pressure in intake maijfold 6 is less than the pressure in chambers 30 and 3|, that is, when a greater suction'prevails in the intake manifold 45 than in the booster device, valves 4| and 42 will be held constantly open so that the suction of the intake manifold will be applied directly to tubes 35 and 31. On the other hand, when thepressure in the intake manifold exceeds that in chambers 30 and 3|, that is, when the engine intake suction drops excessively, valves 4| and 42 will open and close alternately in consonance with the cam impelled movements of diaphragm 2| and the device functi; ns a suctionpump.

ning mixture.

Thus the suction applied to suction operated auxiliaries such as windshield wiper 36 and also suction piston l6 will be prevented from dropping below a predetermined minimum.

The thermostat l2, when cold, urges finger l and arm 9 in a counterclockwise direction so as to close the choke valve. In cranking during cold starting, suction applied to piston 16 is insufiicient to counteract the thermostatic pressure and afi'ect the choke valve. However, when the engine fires, the intake suction increases immediately causing piston Hi to be drawn downwardly and rotating arm 8 clockwise so as to open the choke valve against the pressure of the thermostat to provide a suitably leanrun- The thermostat, when heated, tends to unwind so as to decrease, and eventually eliminate, its resistance to opening of the choke. Piston that some of the suction supplied through tube 31 is efl'ective to draw heated gases from stove I 8 through tube is and housing 8, past piston I6 and thence through the booster pump and into the intake manifold. As above explained, the booster device prevents suction applied through tube 31 from dropping below a predetermined minimum, thus insuring an adequate flow of heated gases through the thermostatic housing at all times during operation of the engine.

The above described automatic choke mechanism is more fully described and claimed in a co-pending application in the name of the pres- |6 fits rather loosely in cylinder I! so ent inventor, Serial No. 134,070, filed March 31, 1937. The hot spot and manifold construction and the carburetor are merely illustrative and may be constructed in any suitable manner. Also the suction booster device, per se, is of a previously known type. The above and other features of the illustrated structure may be modifled in various respects as will occur to those skilled in the art and the exclusive use of all such modifications as come within the scope of the appended claims is contemplated.

I claim:

1. In an internal combustion engine having an intake system, a carburetor having a choke valve, choke control mechanism including a thermostat housing, means for supplying heated gases to said housing, and a suction device distinct from said intake system and connected to said housing so as to draw heated gases therethrough from said means.v

2. In an internal combustion engine, an intake manifold, a carburetor connected thereto and including a choke valve, choke control mechanism including a thermostat housing, means for supplying heated gases to said housing, and a suction pump device connected to said intake manifold and said housing for drawing heated gases from said means through said housing when the pressure in said manifold exceeds that in said device.

IRVEN E. COFFEY. 

